1. Field of the Invention
The present invention relates to a method for obtaining a polyol-containing homogeneous liquid composition from a rigid polyurethane foam in a short time. The polyol-containing homogeneous liquid composition forms a one-layered liquid substantially composed of polyol, and can be directly reused as a polyol component for the production of rigid polyurethane foam.
2. Description of the Prior Art
There have been proposed various methods for recovering polyol from a polyurethane foam by the degradation of the polyurethane. Among them, the method disclosed in U.S. Pat. No. 3,404,103 is particularly excellent. In this method, a polyurethane foam is thermally degraded in a mixture system composed of an alkaline solution added with an amine compound. However, this method has the drawback that the recovered degradation product forms two layers and cannot be directly reused as a raw material for polyurethane foam, and the polyol component must be separated and recovered from the recovered degradation product and then reused for the production of polyurethane foam. Further, there are disclosed in Japanese Patent Laid Open Specification No. 28,407/73 and No. 93,696/73 methods wherein waste polyurethane or polyisocyanurate foam is degraded in the presence of two kinds of dihydroxy-compounds composed of an aliphatic diol and a dialkanolamine, and is recovered in the form of polyol. However, in these methods, a long time is required for the degradation, and a particularly long time is required for the degradation at a low temperature.